This invention relates to a control apparatus for a vehicle, including a RAM adapted to require a power to store and retain data, a nonvolatile memory adapted not to require a power to store and retain data, a CPU adapted to watch and/or control an engine and/or an automatic transmission based on data stored in the above-mentioned RAM.
As a memory used for storing data, there is one which is called a nonvolatile memory whose data cannot erased even if a power is turned off. Additionally, as a control apparatus for a vehicle employing a so-called learning control by which a suitable control is made based on data stored in the past, there has been proposed a system which is arranged to accomplish the learning control of a suitable line pressure upon determining a deviation of inertia torque during a shift of an automatic transmission for the purpose of lightening a shift shock of the automatic transmission. In this conventional system, a learning correction value for the line pressure control is stored after an ignition switch is turned OFF. Such a technique is disclosed in Japanese Patent Provisional Publication No. 7-243518.
A hardware configuration of a power supply circuit for storage in the above conventional system is schematically illustrated in FIG. 4 in which known techniques such as a A/D converter, a ROM (read-only memory) and the like are omitted for the purpose of simplicity of illustration. The above conventional system includes a transmission controller 100′ arranged to accomplish a shift control of the automatic transmission. The transmission controller 100′ includes a RAM 101′ adapted to require a power to store and retain data, a EEP-ROM (nonvolatile memory) 102′, and a CPU 103′ adapted to watch or control the automatic transmission based on present or past data stored in the RAM 101′. The CPU 103′ is normally adapted to read data accumulated in the RAM so as to accomplish a hydraulic pressure control and a trouble judgment for the automatic transmission. However, when the ignition switch is turned ON, the CPU 103′ is adapted to read data accumulated in the EEP-ROM 102′ so as to initiate processing such as calculation, command and the like based on these data.
A main power (source) or existing battery 110′ is for supplying a power to the transmission controller 100′ (i.e., the RAM 101′, the EEP-ROM 102′ and the CPU 103′). This battery 110′ is the power common to controls for whole the vehicle including an engine, a lock-up torque converter and an automatic transmission. A voltage regulator 111′ is provided to supply a power having a voltage Vcc required by the CPU 103′ when a power is supplied from the battery 110′ to the transmission controller 100′. This voltage regulator 111′ is connected to the battery 110′ through a shutoff circuit 112′ which will be discussed after.
A flowchart illustrating a control processed by the CPU 103′ is shown in FIG. 5. This control is executed every several msec upon trigger of turning-ON of the ignition switch 5′. In FIG. 5, first at a step S11, a rise of an ignition (IGN) voltage Vign at an ignition coil is waited until the ignition voltage Vign exceeds a threshold value V1′ which can satisfy a voltage required for the controls for whole the vehicle. When a decision is made such that the ignition voltage Vign exceeds the threshold value V1′, it is judged that the ignition voltage Vign can satisfy the voltage required for the controls of whole the vehicle, and a flow goes to a step S12 at which the RAM 101′ is initialized.
At a step S13, a memory is checked. When a decision is made such that such memory checking is completed at the step S14, the control goes to a step S15 at which a CAN (Controller Area Network) communication is initiated to enable mutual data communication among electronic control devices mounted on the vehicle. At a step S16, a line pressure PL and the like to be supplied to the automatic transmission are controlled. At a step S17, a shift lock control is made so that a select lever cannot be located to a parking (P) range position if a brake pedal is not depressed.
At a step S18, the flow returns to the step 15 until the ignition voltage is judged to be not higher than V1, thereby continuing the hydraulic pressure control to the automatic transmission. Then, when the ignition voltage Vign is judged to be lower than the threshold value V1 at a step S18, the present or past data are stored to the EEP-ROM 102 from the RAM 101 (i.e., learning and/or trouble codes are written in the EEP-ROM) at a step S19. Thereafter, the flow goes to a step S20 at which a shutoff circuit 112′ is operated thereby shut off the power supply from the main power 110.